This relates generally to displays, and, more particularly, to displays such as liquid crystal displays.
Displays are widely used in electronic devices to display images. Displays such as liquid crystal displays display images by controlling liquid crystal material associated with an array of image pixels. A typical liquid crystal display has a color filter layer and a thin film transistor layer formed between polarizer layers. The color filter layer has an array of pixels each of which includes color filter elements of different colors. The thin film transistor layer contains an array of thin film transistor circuits. The thin film transistor circuits can be adjusted to control the amount and color of light that is produced by each pixel. Thin film transistor circuitry in a typical pixel array includes data lines and gate lines for distributing data and control signals.
A layer of liquid crystal material is interposed between the color filter layer and the thin film transistor layer. During operation, the circuitry of the thin film transistor layer applies signals to an array of electrodes in the thin film transistor layer in response to data and gate line signals. This produces electric fields that extend from each electrode through the liquid crystal layer to an associated portion of a ground plane. The electric fields control the orientation of liquid crystal material in the liquid crystal layer and change how the liquid crystal material affects polarized light.
Each image pixel is characterized by a respective aperture that defines how much light can pass through that image pixel. It can be challenging to maintain uniformity across the image pixels of a display. For example, metal structures such as signal paths are sometimes used to route signals across the display. These metal structures can block some light from passing through some of the image pixels, which reduces the aperture of the affected image pixels. Other image pixels that are not blocked by the metal structures may have apertures that are greater than the apertures of the affected image pixels, which results in non-uniform brightness across the display.
To maintain display brightness uniformity, an opaque grid such as a black matrix can be used to reduce the aperture of all image pixels (e.g., even pixels that are not obstructed by metal structures). However, with reduced pixel apertures, the overall brightness of the display is reduced and the display tends to consume additional power to ensure sufficient brightness levels. It would therefore be desirable to be able to provide improved displays with brightness uniformity.